Both soft and rigid contact lenses require periodic cleaning. Rigid contact lens cleaning and polishing procedures are presently beyond the ability of the normal contact lens wearer and should be done professionally. Motorized cleaning and polishing units are commonly used to accomplish this end. Such units must be carefully used. Too much abrasion through over polishing can alter the optical characteristics of the lens upon excessive removal of material. Excessive heat build up can also damage the lens. The introduction of the gas permeable lenses has greatly benefited the contact lens wearer through increased comfort and corneal health. Maintenance of such lenses is a serious challenge not only for the contact lens wearer, but for the professional practitioner as well. The fragile nature of the lens material makes routine and necessary office cleaning and polishing procedures hazardous. Greater potential for damage to lenses exists through the use of motorized lens treatment apparatus. Harmful heat build up can occur in only a few seconds. A diminished or destroyed wetability property of the rigid gas permeable lens means comfort problems for the wearer. Also, considerable care and skill is necessary to avoid optics blur as well as power changes.
Practitioners presently attempt to polish the rigid gas permeable lens without motorized apparatus by rubbing the lens on a velveteen cloth piece held in the hand or on a flat work area. This method offers no precise control of the pressure exerted on the lens. Plastic is removed unevenly usually resulting in abberation of the lens surfaces. This same method is also used in the cleaning of lenses using a surfactant solution.
Lens modification of the rigid gas permeable lens can also be a hazardous procedure due to the delicate structure of the lens. Rigid lenses have two to five separate radii of curvatrure on the back surface of the lens to provide proper alignment on the cornea and proper tear exchange under the lens. Most of these curves have to do with the periphery of the lens with the central large area of curve being the optical zone. Modification for the most part involves widening, increasing or decreasing the radii of curvature of peripheral curves on the lens.
Soft contact lenses are beset by cleaning problems not encountered with rigid lenses because by their nature they are prone to lipid and protein coating rendering them extremely difficult to clean. The fragile nature of the lens precludes the use of solvents or strong chemical cleansers. The most common method still involves daily digital cleaning with a surfactant cleaner in conjunction with weekly enzyme cleaning. However the skin is a poor cleaning surface with a texture unable to provide a scrubbing or brushing action suitable for cleaning the lens surface.